TOYOTA MIRAI 2018 (in English) Manual Online

812. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U■
Regenerative braking
In the following situations, the vehicle generates electricity from the decelera-
tion of the vehicle while driving.
● The accelerator pedal is released while driving with the shift position in D.
● The brake pedal is depressed while driving with the shift posit ion in D.
■ Charging the traction battery
Because electricity generated by the fuel cell stack and regene rative braking
charges the traction battery, the battery does not need to be c harged from an
outside source. However, if the vehicle is left parked for a lo ng time, the trac-
tion battery will slowly discharge. For this reason, be sure to drive the vehicle
at least once every few months for at least 30 minutes or 10 mi les (16 km).
If the traction battery becomes fully discharged and you are unable to start
the fuel cell system, contact your Toyota dealer.
■ Charging the 12-volt battery
P. 403
■ Parking
Because there is no engine sound or vibration, it is easy to mistake the fuel
cell vehicle for being off when it is actually still running, as indicated by the
“READY” indicator being illuminated. For safety, make sure to a lways shift the
shift position to P and apply the parking brake when parked.
■ Maintenance, repair, recycling, and disposal
Contact your Toyota dealer regarding maintenance, repair, recyc ling, and dis-
posal. Do not dispose of the vehicle or any of its components y ourself.
• Humming sound
• High pitch soundOperation of the motor
Sounds may come from the motor com-
partment.
(In particular, sounds may be heard when
accelerating or decelerating.)
Blowing and draining soundExhaust water or air is being purgedSounds may come from the rear of the
vehicle.
May also occur periodically while parked
when it is cold to prevent freezing.
(Sounds may be heard when vehicle is
stopped, fuel cell system is stopped, park-
ing.)
Noticeable soundsSource of the sounds

822. Fuel cell vehicle
MIRAI_OM_USA_OM62025U
Fuel cell vehicle precautions
The fuel cell vehicle has hydrogen tanks (10150 psi [70 MPa,
714 kgf/cm2, 700 bar]), fuel cell stack, and hydrogen pipelines as
hydrogen-related components. Pay attention to all warning label s
attached to the vehicle.
This diagram is for illustrative purposes only and may differ f rom the
actual vehicle.
Hydrogen-related components
Warning label
Hydrogen detectors
Fuel cell stack Hydrogen tanks
Hydrogen tank valves
Hydrogen pipelines

832. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U
The fuel cell vehicle has high-voltage components (about 650 V m axi-
mum) such as a fuel cell stack, traction battery, power control unit,
high-voltage cables (which are di stinguished from low-voltage cables
by their orange covers), electric motor (traction motor), etc., and high-
temperature parts such as the radiator for cooling. Pay attenti on to all
warning labels attached to the vehicle.
This diagram is for illustrative purposes only and may differ f rom the
actual vehicle.
High-voltage and high-temperature components
Warning label
Power control unit
High-voltage cables (orange)
Fuel cell stack
Traction battery
Service plug
Fuel cell converter Electric motor (traction motor)
Air conditioning compressor
Radiator for inverter cooling
Radiator for fuel cell stack
cooling
Auxiliary inverter
Cabin coolant heater

842. Fuel cell vehicle
MIRAI_OM_USA_OM62025U
When a certain level of impact from an accident is detected, the fuel
cell system is shut down and the system shuts out the high voltage.
Also, the fuel supply is stopped from the hydrogen tank valves. If the
emergency shut off system activates, your vehicle will not rest art. To
restart the fuel cell system, contact your Toyota dealer.
A message is automatically displ ayed when a malfunction occurs in
the fuel cell system or an im proper operation is attempted.
If a warning message is shown on
the multi-information display, read
the message and follow the
instructions. ( P. 376)
Fuel cell vehicles do not have engine sounds like gasoline vehi cles.
Therefore, it makes an artificial noise at low speeds to notify pedestri-
ans and nearby vehicles that it is approaching. The sound varie s with
speed and will stop whe n the vehicle exceeds approximately 15 mp h
(25 km/h).
Emergency shut off system
Fuel cell warning message
Vehicle proximity notification system

852. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U
There is an air intake vent beside
the rear left seat for the purpose
of cooling the traction battery. If
the air intake vent is blocked, it
could lead to a reduction in trac-
tion battery output.
■If a warning light comes on, a warning message is displayed, or the
12-volt battery connection is disconnected
The fuel cell system may not be able to restart.
If the “READY” indicator does not come on, even when the start procedure is
repeated, contact your Toyota dealer.
■ If “Hydrogen Leakage Detected Visit Your Dealer” is displayed on the
multi-information display
A small amount of hydrogen gas may be leaking. Have the vehicle inspected
immediately at the nearest Toyota dealer.
■ If “FC System Shutdown due to Hydrogen Leakage Stop Your Vehicle in
a Safe Place and Contact Your Dealer” is displayed on the multi -informa-
tion display
● Hydrogen gas may be leaking.
When hydrogen gas is leaking or some other malfunction is detected:
P. 90
● The air conditioning system will shut off automatically.
■ Running out of fuel
When the vehicle has run out of fuel and the fuel cell system c annot be
started, refuel the vehicle until the low fuel level warning li ght (P. 371) turns
off before trying to restart. It may not be able to restart if the refueled amount
is too low (less than about 2.7 lb. [1.2 kg]).
Traction battery air intake vent

862. Fuel cell vehicle
MIRAI_OM_USA_OM62025U■
Fuel cell stack
●Depending on the usage environment, the fuel cell power output may
decline over the life of the vehicle. However, this will have almost no effect
on driving performance.
● In the following situations, the fuel cell power output may dec line faster than
normal driving:
• Extended use in areas with high amounts of dust
• Extended use in areas with high levels of sulfur (such as volc anoes or hot
springs).
• Extended use in areas with high concentrations of the following substances:
-Organic solvents, such as paint and thinner
-Amine-related materials such as ammonia
-Chlorinated substances such as salt air and snow-melting agent
However, upon returning to normal environment, the fuel cell po wer output
will recover over time.
• Salt water gets into the air cleaner filter It is recommended to replace the air cleaner filter and clean t he surround-
ing components. Have the vehicle inspected at your Toyota deale r
• The number of times the fuel cell system is started and stoppe d is exces-
sively high
• Extended use in freezing temperatures
■ Hydrogen tanks
●The hydrogen tanks are the high-pressure storage containers that are filled
with compressed hydrogen gas. The vehicle can be refueled at hy drogen
stations.
● The hydrogen tanks have an expiration date. Vehicles with expir ed hydro-
gen tanks must not be driven or refueled until the hydrogen tanks are
replaced. The expiration date is written on the inside of the fuel door. Con-
sult your Toyota dealer.
● When disposing of the hydrogen tanks or the hydrogen tank valve s, consult
your Toyota dealer for details.

872. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U■
Fuel cell stack coolant
●Fuel cell stack coolant uses a specifically-designed fluid with high electrical
insulation properties, in order to safely cool the high-voltage fuel cell stack.
● Never add water or other coolants to the fuel cell stack coolin g system, as
they will cause permanent damage.
● Consult your Toyota dealer for replenishing or changing the fue l cell stack
coolant.
■ Ion filter
●An ion filter is installed in the coolant lines for the fuel ce ll stack, in order to
maintain the normal insulation properties of the coolant.
● It is necessary to periodically change the ion filter. ( P. 378) Contact your
Toyota dealer for this periodic maintenance.
■ Tailpipe
●When the power switch is turned off and the fuel cell system is stopped
( P. 173) after driving, exhaust water is discharged. Be careful w hen stand-
ing behind the vehicle to avoid dripping or spraying.
● It is possible to manually purge the exhaust. This may be desirable, for
instance, before parking in a garage. This is done by pressing the H
2O
switch. ( P. 173)
● On cold days, water vapor in the exhaust may appear as a white mist emit-
ted from the tailpipe. This is not a malfunction.
● If the tailpipe is blocked, the fuel cell system will stop.
■ Hydrogen detectors
When the power switch is turned to ON mode, the hydrogen detect ors are
activated.

882. Fuel cell vehicle
MIRAI_OM_USA_OM62025U■
Power output restriction
When the power output is restricted, the vehicle may fail to accelerate or even
decelerate, even though the accelerator pedal is depressed. If a safe driving
speed cannot be maintained, stop the vehicle in a safe place aw ay from the
traffic. This may be caused by the following conditions:
● The coolant temperature may be too high. This can be caused by driving
conditions such as repeated sudden acceleration and deceleratio n, continu-
ous driving on an incline, continuous driving at high altitudes with a high
load, etc. In such situations, the power output restriction ind icator (amber) is
displayed on the main display, “High FC Temperature Reduced Power” is
displayed on the multi-information display, and the power outpu t is
restricted. Once the coolant returns to normal temperature, the power out-
put will return to normal. ( P. 377)
● The remaining fuel may be low. After the low fuel warning indicator comes
on, the output power will be gradually restricted in order to extend the possi-
ble driving distance. Once getting to this point, the remaining driving dis-
tance possible is short. Immediately refill the vehicle with hy drogen.
● On cold days, the low fuel warning indicator comes on faster than usual and
the output power is restricted.
■ Vehicle proximity notification system
In the following cases, the vehicle proximity notification syst em may be diffi-
cult to hear for people around.
● In very noisy areas
● In wind or rain
Also, because the vehicle proximity notification system is loca ted in the front
of the vehicle, it may be more difficult to hear from the rear of the vehicle
compared to the front.
■ Electromagnetic waves (EMF)
●High-voltage parts and cables in fuel cell vehicles have an ele ctromagnetic
shielding configuration, and therefore emit approximately the s ame amount
of electromagnetic waves as conventional gasoline-powered vehicles or
home electronic appliances.
● Your vehicle may cause sound interference in some third party-p roduced
radio parts.
■ Traction battery
The traction battery has a limited service life. The lifespan of the traction bat-
tery can change according to driving style and driving conditio ns.

892. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U■
Hydrogen Gas Characteristics
●Hydrogen gas ignites more easily than gasoline. However, it is lighter than
air and disperses quickly. So even if hydrogen were to leak from the system,
it would quickly dilute until it is no longer flammable.
● As with gasoline and natural gas, hydrogen gas is not dangerous if it is han-
dled properly. Thoroughly read and understand the characteristi cs shown in
the table below.
Hydrogen gas
LPG
(Liquid Petroleum Gas)
Gasoline
Normal stateGaseous
(Lighter than air)Gaseous
(Heavier than air)
Volatile liquid
(evaporates
easily)
(Heavier than air)
Ease of
ignitionEasier than
gasolineAt the same level
as gasoline—
Ease of
accumulation
• Disperses
upward and is
diluted to safe
concentrations
in open air
• Does not adhere to
clothing
• Spreads on the
ground or floor
• Does not adhere to
clothing• Spreads on theground or floor
• Adheres to clothing
Detectability
•Due to itscolorless and
odorless state,
difficult to detect
by sight or smell
• Vehicle
hydrogen
detectors will
display a
warning on the
multi-
information
display
• Detectable by odor and gas
leaking noise• Detectable bycolor and odor

902. Fuel cell vehicle
MIRAI_OM_USA_OM62025U■
Basic concepts of hydrogen safety
●Prevent leakage
The pipe joints of the hydrogen pipelines are designed to preve nt leaks.
The joints are checked for gas leakage at every official vehicle inspection.
● Detect to stop leakage
• The vehicle is equipped with hydrogen detectors. If the hydrog en detec-
tors detect a leak, the hydrogen tank valves automatically clos e to pre-
vent more hydrogen from escaping.
• The vehicle is equipped with a collision sensor. If the collis ion sensor
detects a collision, the hydrogen tank valves automatically clo se to pre-
vent hydrogen gas from leaking from any damaged components.
● Disperse the leaked hydrogen gas
The hydrogen tanks and pipelines are located outside of the passenger
compartment, so any leaked gas will disperse into the atmospher e by
design.
● Eliminate sources of fire
No source of fire is located near the hydrogen pipelines by des ign.
WARNING
■Hydrogen-related components
● Never alter, customize, or disassemble any hydrogen-related par ts.
● The hydrogen tanks, fuel cell stack, hydrogen pipelines, and co nnecting
components are filled with hydrogen gas. Do not remove or disassemble
these parts. Doing so can cause a hydrogen gas leak, resulting in fire or
explosion of the vehicle, which may result in death or serious injury.
■ When hydrogen gas leak or other malfunction is detected
● If you notice gas leaking noises or any other malfunction, imme diately stop
the vehicle in a safe, well-ventilated place.
● If a warning message is shown on the multi-information display, immedi-
ately stop the vehicle in a safe, well-ventilated place.
● If a large amount of hydrogen gas leaking is noticed, turn off the power
switch, exit the vehicle, and stay far away from it. Display wa rning signs
and keep sources of fire away from the vehicle. If possible, get assistance.
When the above is done, immediately contact your Toyota dealer.